1. Field of the Invention
The invention relates to new thermoplastic molding materials based on impact resistant styrene polymers containing polyphenylene ethers.
2. Prior Art
Thermoplastic materials which are suited for the manufacture of molded parts and which contain impact resistant styrene polymers employing a rubber and further containing polyphenylene ether are described, for instance, in U.S. Pat. Nos. 3,383,435; 4,128,602 and 4,128,603. Such molding materials are suited for the manufacture of molded parts which have a better dimensional stability when exposed to heat compared to those produced of impact resistant styrene polymers which are not mixed with polyphenylene ethers. Molding materials which contain linear or star-shaped hydrogenated styrene containing block copolymers in addition to the impact resistant polymers and polyphenylene ethers have also been described (for example, U.S. Pat. No. 4,167,507). Molded parts with particularly high impact resistance can be produced from these molding materials. While the physical properties are generally satisfactory, it has been found that the molding masses have unfavorable flow characteristics. In these prior art molding masses the flexible component of the impact resistant styrene polymer has a particle size distribution in the range of 0.8 micron to 2 microns.
The purpose of this invention was therefore the development of thermoplastic molding materials based on impact resistant styrene polymers and polyphenylene ethers which can be processed into molded parts with particularly high impact resistance and which have improved flow characteristics. This purpose is met by the molding materials of this invention which contain an impact resistant styrene polymer, a block copolymer containing a hydrogenated impact resistant styrene, and polyphenylene ether.